I don't think even a 150 would heat that big of an enclosure enough. I would recommend a RHP instead. Look in to getting one of those, they are more expensive, but it will last 10 years or so and are designed to heat larger enclosures like yours better. Get a thermostat for it as well, even if you do decide to try a CHE. The more watts you use, the less it has to work to heat up the area, but you MUST use a thermostat or you will overheat the enclosure.